Combustion with fluidization and after-burning



June 16, 1964 J. 6. WILSON ETAL COMBUSTION WITH FLUIDIZATION ANDAFTER-BURNING ox iginal Filed June 1, 1959 2 Sheets-Sheet 1 INVENTORSJOSEPH G. WILSON ROBERT F. DUTTON TERRELL W. HAYMES JU TIN C. DYGERTTHEIR ATTORNEY June 16, 1964 J. G. WILSON ETAL COMBUSTION WITHFLUIDIZATION AND AFTER-BURNING 2 Sheets-Sheet 2 Original Filed June 1,1959 INVENTORS JOSEPH 6. WILSON ROBERT F. DUTTON TERRELL W. HAYMESJUSTIN c. DYGERT BY:

THEIR ATTORNEY United States Patent 3,137,133 COMBUSTION WITHFLUIDIZATION AND AFTER-BURNKNG Joseph G. Wilson, Riverside, Conn, RobertF. Button, Long Beach, Calif., Terrell W. Haymes, Darien, Conn, andJustin C. Dygert, Walnut Creek, Calif., assignors to Sheil Oil Company,New York, N.Y., a corporation of Delaware Continuation of applicationSer. No. 817,420, June 1, 1959. This application Jan. 17, 1964, Ser. No.341,825 10 Claims. (Cl. 60-3902) This is a continuation of ourapplication Serial No. 817,420, filed June 1, 1959, now abandoned,which, in turn, was a continuation-in-part of application Serial No.747,007 filed July 7, 1958, now abandoned.

The invention relates to the combustion of fuel in a fluidization bed offinely divided solids wherein the fuel is partly burned to produce exitgas which contains carbon dioxide and carbon monoxide together withentrained solids and is incapable of self-sustained normal combustion atthe exit temperature when commingled with supplemental air. (Theexpression normal combustion is used to denote combustion without eitherheating, as by a flame which consumes supplemental fuel, or by contactwith an oxidation-promoting catalyst.) The solids which are fluidizedmay, for example, be non-combustible or combustible bodies with whichthe fuel is combined naturally or artificially either prior to or duringthe combustion, e.g., metal oxide cracking catalyst bearing carbonaceousdeposits which are burned, comminuted coal or coke, or material whichsupplies oxygen for the combustion, e.g., ore to be reduced. 1

More particularly, the invention relates to an improvement in such acombustion wherein energy is recovered from the said exit gas by furtherburning it in a boiler after adding supplemental air oroxygen-containing gas (for convenience hereinafter called supplementalair), expanding the gas in a turbine, and utilizing the resulting shaftpower to drive a compressor which supplies at least the fluidizing gasand, preferably, also the supplemental air, whereby the plant can beself-powered.

Examples of applications are: (l) the burning of carbonaceous depositson powdered contacting agents, particularly cracking catalyst consistingof metal oxides which were used in cracking hydrocarbon oils, toregenerate the contacting agents; (2) the burning of oil contained inoil-bearing diatomaceous earth to produce light-weight aggregate; (3)the burning of fly ash which is produced when powdered coal is consumedin a furnace and which still contains oxidizable fuel; (4) the burningof ash which is produced when shale oil is retorted, the said ashcontaining carbonaceous constituents; (5) the burning of limestone whichis admixed with coal, soot or coke for the production of lime; (6) theburning of finely-subdivided coke; and (7) reduction of finely-dividedmetal ores, such as iron ore, by a reducing agent, such as a hydrocarbonoil or combustible gas, e.g., methane. All but the last two examplesinvolve the combustion of lowgrade fuel; the lime constitutes the solidmaterial, produced in situ in the process is the fifth example; the fuelitself is the solid material in the sixth example; and in the lastexample the reducing agent is the fuel, which is oxidized by the ore. Inall but the last example the oxidizing agent is contained in thefluidizing gas and in the last example the fuel constitutes or is aconstituent of the fluidizing gas.

Such combustions as the foregoing can be effected in a fluidizationchamber containing the solid particles through which a fluidizing gas ispassed upwards at a rate to maintain the particles as a fluidized bed,i.e., in a turbulent state with quasi-liquid properties, including arecognizable upper ice level. Depending upon the system, the fluidizinggas may contain the oxidant and/or the fuel. The fuel is partiallyburned to form gaseous combustion products which emerge from the top ofthe fluidized bed together with entrained solids and unreactedfluidizing gas, such as nitrogen or other inert gas. Because thefluidizing gas is usually air in cases wherein the oxidant is a gas itwill, for brevity, be usually so called herein, it being understood thatthe word is intended to have a generic connotation and that theinvention is applicable also to the case wherein the fuel constitutes oris a part of the fluidizing gas.

Complete oxidation of such fuel to carbon dioxide in such a fluidizedburning operation is usually not feasible. Incomplete combustion isoften the result of the use of only a limited amount of air to avoidexcessive compression costs as well as to control the temperature in thefluidized bed. For example, in the regeneration of catalyst, such assilica-alumina particles, which was used in the cracking ofhydrocarbons, the temperature in the fluidized bed must be sufficientlyhigh to maintain combustion, e.g., above 650 F., but temperatures above1050 F. to

0 F. often cause deterioration of the catalyst. Higher temperatures areusually undesirable for the further reason that the gas emerging fromthe fluidized bed inherently entrains solid particles which must beseparated not only to conserve the solids and avoid air pollution butalso to prevent injury to the boiler and, in the present invention, tothe blades of the turbine. Excessively high temperatures lead to rapiddeterioration of cyclones and similar separators which are used to cleanthis gas. Complete combustion of the fuel in the fluidized bed is,moreover, often not possible with reasonable amounts of air because theexit gas is in equilibrium with freshly charged fuel in cases in whichthe process is carried out by con tinuously feeding the charge anddischarging the solid particles.

Such fluidized combustion processes require large-volume streams ofcompressed fluidizing gas which has heretofore been supplied bycompressors consuming extaneous power. Although some of the sensibleheat and fuel value of the exit gas has heretofore been recovered toproduce steam, this has not been sufficient to meet the compressionrequirements but has involved continuing power consumption forcompression.

It is the object of this invention to effect a saving in compressioncosts in carrying out such a combustion in a fluidized bed of solids byrecovering a greater amount of energy from the exit gas by addingsupplemental air and further burning the carbon monoxide in a boiler togenerate steam or other vapor and utilizing the exit gas to operate aturbine-compressor set which compresses sufficient gas to meet at leastthe fluidizing gas needs and, preferably, also the supplemental airrequirements of the process.

A further object is to provide an improved integrated plant for carryingout a combustion in a fluidized bed of solids which includes afluidization-combustion chamber for incomplete combustion of the fuel,an inertial separator for removing entrained solids from exit gaswithout substantial drop in the gas temperature, a carbon monoxideboiler (also known as a waste-gas boiler), and an expansionturbine-compressor set which is operated on the clean exit gas(preferably, but not necessarily, after passage through the boiler) andcan meet the compression requirements of the plant. Ancillary objectsare to provide an improved plant which is economical in operation andcapital costs; which uses simple controls; and which can be installed ona small plot area.

Additional objects will become apparent from the following descriptionvIn summary, according to the preferred embodiment of the invention, themass'of divided solids containing fuel and a fuel oxidant as reactantsis confined in a fluidization-combustion .chamber at a substantialsuperatmospheric pressure suflicient to permit expansion of exit gastherefrom in a turbine, and a fluidizing gas containing one of saidreactants (fuel or oxygen) is passed upwards through the bed to fluidizethe solids and effect partial combustion of the fuel with the productionof combusted gas which contains carbon dioxide and carbon monoxide butis incapable of self-sustained, normal combustion at the exittemperature when admixed with supplemental air; the solids are, in mostapplications, supplied to and/or removed from the chamber continuouslyor intermittently during the combustion; the said combusted gas emergesfrom the fluidized bed and is freed from entrained solids withoutmaterially lowering its temperature in an inertial type separator,preferably a series of cyclones; the resulting clean gas is mixed withsupplemental air and subjected in a supercharged carbon monoxide boilerto oxidizing conditions causing further burning wherein the carbonmonoxide is oxidized to carbon dioxide, either by heating with anauxiliary fuel burner and/ or by contact with a catalyst, the transferheat to the boiler tubes by radiation and convection; the resultingcombustion products are discharged from the boiler and passed through anexpansion gas turbine which is coupled to a compressor wherein thefiuidizing gas and supplemental air are compressed.

The invention will be described in detail with reference to theaccompanying drawings forming a part of this specification and showingdiagrammatically, by Way of illustration, a specific embodiment suitablefor the regeneration of carbonized, finely-divided catalyst, and amodification wherein:

FIGURE 1 is a front elevation view of the apparatus, parts being brokenaway;

FIGURE 2 is an enlarged sectional view, taken on the line 2-2 of FIGURE1;

FIGURE 3 is an enlarged fragmentary sectional side elevation of theboiler;

FIGURE 4 is an enlarged fragmentary sectional view of the boiler; and

FIGURE 5 is a fragmentary sectional view of the lower part of theboiler, showing a modification wherein a catalyst is employed.

Referring to the drawings, the principal parts of the apparatus are: avertically elongated fluidization-combustion chamber provided with afluidizing air inlet pipe 11, which is connected to a bed airdistributor 12 situated within the lower part of the chamber, andcontaining within the upper part a series of inertial-type separators13; a supercharged boiler having a boiler housing 14 mounted on top ofthe chamber 10 and containing an auxiliary fuel burner 15 and boilertubes, some of which are shown diagrammatically at 16, connected to asteam drum 17; and one or more, e.g., a pair of expansion gas turbines18, 18a, each having a direct drive connection to a correspondingcompressor 19 or 19a.

It will be understood that although the drawings show only oneturbine-compressor set 18-19 for supplying fluidizing air and only oneset 18a-19a for supplemental air, a plurality of such sets may beemployed for each purpose. The turbines and compressors are preferablymounted at the top of the fluidizing chamber, as shown.

a The fluidization-combustion .chamber 10, which has suflicient strengthto confine gas under substantial superatmospheric pressure, such as 15to 35 pounds per square inch gage, is mounted on a support structure 20and has a frusto-conical bottom 21 which is open at the bottom andconnected to a solids discharge pipe 22 fitted with a slide valve 23. Ariser feed pipe 24 extends upwards through the bottom and receives thecarbonized catalyst charge from a standpipe 25 and pressurized lift airis supplied, either from the pipe 11 or from an extraneous source, notshown, through a pipe 26. The feed pipe dis- 4.- charges against adeflector 27. The upper part of the chamber is enlarged as shown at 23to accommodate the separators and has a top closure wall 29.

The inertial separators include a plurality, e.g., three stages ofcyclones arranged in series. It will be understood that any desirednumber, e.g., one to six, of cyclones may be used for each stage. Eachfirst-stage cyclone St) has an intake 31 positioned to receive gas abovethe top of the fluidized bed, indicated at L, a solids outlet pipe 32which extends down'into the fluidized bed in the form of a dipleg, and agas outlet duct 33 which is connected to the intake of a second-stagecyclone 34. Each secondstage cyclone also has a solids outlet pipe 35extending into the fluidized bed and a gas outlet pipe 36 whichdischarges gas into a distributing chamber 37 between the closure wall29 and a transverse partition 38. The central part 38a of this partitionis upwardly convex or dished for structural reasons and supports a largenumber, e.g., ten to sixty, of small, third-stage cyclones having outertubes 39 which extend through the partition. In the embodiment shown(FIGURE 2), each third-stage cyclone includes, further, a smaller,concentric gas outlet tube 40 which is fitted to a hole in the closurewall 29 and swirl vanes 41 in the annular space between the tubes.Solids, together with some bleed gas, are discharged at or near thebottoms of the tubes 3E through slits 42, which may be surrounded byskirts 43, into a collecting chamber 44 defined by a hopper 45; theseparated solids and bleed gas are discharged through a solids dischargeduct 46 which extend out through the wall of the chamber 10.

The boiler housing 14 (FIGURE 4) is also constructed to contain gas atthe superatmospheric pressure noted above. It contains a refractorycasing 47 which extends upwards from the burner 15 and defines anauxiliary combustion chamber. An auxiliary fuel, such as fuel gas, issupplied to the burner by a fuel pipe 48. The burner includes an air box49 to which supplemental combustion air is supplied through an air pipe50 from the compressor 1% in amount sufficient to burn the auxiliaryfuel and the carbonmonoxide in the gas flowing from the fluidizationchamber through the third stage cyclones. The bottom of the combustionchamber is peripherally closed at the outer-most part by a wall 51 andthe air box has a mouth 52 directed into the central opening in the wall51, but spaced therefrom to permit gas from the fluidization chamber toflow as an annular stream about the flame from the burner.

The boiler tubes 16 are connected at the bottom to a header 53 which isconnected by an external pipe 54 to the steam drum 17. The upper ends ofthe tubes are connected to the steam drum through a header 55 and pipes56. Feed water to the steam drum is admitted through pipes 57 and 57afrom economizers 58 and 58a described hereinafter, and steam isdischarged through a pipe 59.

Heat is also abstracted from the fluidized bed by means of a bed coil 60which is mounted in the lower part of the chamber 10. Water from thesteam drum is fed to this coil through a'pipe 61 and a circulating pump62, which can be operated ata variable speed, and steam flows to thedrum through a pipe 63. In addition to generating steam, this, coilserves to control the bed temperature.

The hot combustion products emerging from the top of the burner 15 arecommingled with the gas from the fluidization chamber, which enter thecombustion chamber as an annular stream. .The carbon monoxide is therebyheated sufliciently to cause oxidation to carbon dioxide. The resultingcombusted gases emerge from the top of the combustion chamber and flowupwards through a radiant section defined by water wall tubes backed upby a thin metal wall 64. They leave this section through a throat 65 andflow thence radially outward through a superheater section and downwardsthrough an annular convection section 66, imparting heat to the tubes.The gases leave the boiler through gas outlets 6'7 and 68 and flowthrough gas ducts 69 and 69a to the turbines 18 and 18a, respectively.These gas ducts may have emergency shut off valves 70 or 70a and nozzles71 or 71a through which a coolant, such as water or steam can beinjected under control of valves 72 and 72a to maintain a safetemperature at the turbine intake. The latter valves may be operatedautomatically by a temperature controller as shown for the turbine 18aat 73, having a sensing element at the turbine intake and connected tovalve operators 74.

Suitable vent means are provided to vent the hot gas so as to limit thepressure in the boiler and fluidizationcombustion chamber and, thereby,the power input to the turbines; thus, there can be a single vent stack75 connected to the boiler housing and provided with a throttling ventvalve 76. The vent valve is operated to vent gas as required; forexample, it may be operated manually or by any of a variety of automaticcontrols.

In one specific arrangement, a pressure controller 77 having apressure-sensing element in the boiler is connected to a valve operator78 to vent the amount of gas required to maintain a constant pressure inthe boiler and, hence, in the fluidization chamber and at the turbineinlets.

The expanded and partially cooled gas from the turbines flows throughthe economizers 58 and 5811, which include housings for the passage ofgas and contain feed water pipes.

The compressor 19 has the discharge thereof connected to the air inletpipe 11 to supply combustion and fiuidization air to the bed airdistributor 12. The pipe 11 has a vent 79 controlled by a valve 80through which compressed air is vented as required to regulate thetemperature within the fluidization-combustion chamber by limiting therate of air admission. The vent valve 80 can be operated manually orautomatically by any of a variety of controls. For example, the pipe 11may be provided with a flow-measuring device 81 which is connected to aflow controller 82 which is adjustable to permit the desired rate ofair-flow and has its output connected to a valve operator 83. Anydesired constant rate of air flow can thereby be maintained. A similarvent 84,vent valve 85, flow-measuring element 86, flow controller 87 andvalve operator 88 may be provided in the supplemental air pipe 50, toregulate the air-flow to the boiler.

The inlet pipe 11 may further be provided with a valve 89 and a branchpipe 90, having a valve 91, for introducing air from an extraneoussource during start-up. Similarly, the air pipe 50 may have a valve 92and branch pipe 93 provided with a valve 94 for initial supply ofsupplemental air. However, initial air can be obtained by running thegas turbines on steam during start-up.

' The fluidization-combustion chamber is optionally provided with aplurality of nozzles 95 through which quench fluid, such as steam orwater can be injected into the upper part of the chamber from a supplypipe 96 under control of a valve 97 to check after-burning. It will beunderstood that the chamber will be provided with other control means,such as means for indicating the height of the fluidized bed and the bedtemperature and pressure; these instruments, being well known per se,are not shown.

" In operation, as applied for example to the regeneration of carbonizedcracking catalyst most of which passes a US. "standard IOO-mesh screen,the catalyst is admitted continuously through the riser pipe 24, usinglift air from the pipe 26 in an amount of the order of of the fiuidizingair. The catalyst is fluidized by fluidizing air admitted through thepipe 11; initially this air is admitted through the branch pipe 90,valve 89 being closed and valve 91 being open. The catalyst particlesare fluidized to a level L. The fuel, in the form of carbonaceousdeposits on the catalyst particles, is gasified by incomplete combustionand the formation of carbon 'of carbon dioxide to carbon monoxide isabout 1.5 and the regenerator gas contains 5-10 mol percent pt carbonmonoxide, the remainder being inert gas consisting predominantly ofnitrogen and steam. Regenerated catalyst is discharged continuouslythrough the pipe 22 and valve 23. The temperature within the chamber 10is regulated in part by circulating water through the bed C011 60 at arate determined by the pump62 and also by controlling the amount of airadmitted through the pipe 11. The conditions may, for example, becontrolled so that the gas emerging from the top of the fluidized bedhas a temperature of 1050 F. and a pressure of 23 pounds per square inchgage.

The gases emerging from the fluidized bed often contain small amounts ofunconsumed oxygen. In the space above the bed, Where the concentrationof the high heatcapacity solids is low, there is a possibility offurther reaction of this oxygen with the carbon monoxide, known asafterburning, which would result in an uncontrolled temperature rise anddamage to the cyclones. This can be prevented by injecting a quenchfluid through the nozzles 95.

Coarse catalyst particles entrained by the gas from the bed areseparated in the firstand second-stage cyclones 30 and 34 and returnedto the bed through the diplegs 32 and 35 and gas, containing only veryfine particles, at a temperature of 1050 F. and a pressure of 20 poundsper square inch gage, enter the distributing chamber 37. The gas flowsthence through the thirdstage cyclones 3943, which remove catalyst finesto the extent required to prevent damage to the boiler and turbineblades. These fine particles are usually so small as to be useless incatalytic cracking and are discharged through the duct 46. The cleangas, still essentially at the stated temperature and at a pressure of 18pounds per square inch gage, are discharged through the tubes 40 intothe boiler. This boiler is operated at a fire box pressure ofapproximately the pressure of the clean gas.

In the boiler the clean gas is mixed with supplemental air suppliedthrough the pipe 50 in amount to burn the carbon monoxide. The resultingmixture of gases has too low a calorific value for self-sustained normalcombustion at the prevailing pressure and temperature. To effect burningits temperature is raised to about 1400 F. to 1650 F. to createconditions at which the carbon monoxide is oxidized by self-sustainedcombustion. This heating is efiected by burning auxiliary fuel in theburner 15. The flame or radiant gas emanating from the casing 47 impartsheat to the water in the tubes 16 by radiation and convection. Thecombustion products are thereby cooled to a temperature of about 1000 F.to 1150 F. before entering the gas ducts 69 and 69a. The gases areadmitted to the turbines 18 and 18a at about 16 pounds per square inchgage and are expanded therein to produce shaft work. The turbines, inturn, drive the compressors 19 and 19a, which supply fluidization airand supplemental air. When the turbines are in operation, the valve 89is opened and the valve 91 is closed. It will be understood that duringthe start-up period supplemental air may be admitted to the burnerthrough the branch pipe 93; alternatively, the burner may be placed intooperation only after the turbines and compressors are working. Steam maybe used to drive the turbines during start-up.

'The turbine exit gases, at 800 F. and 0.5 pound per square inch gage,are passed through the economizers 58 and 58a, wherein the feed waterabsorbs heat from the gases to preheat the feed Water before the gasesare exhausted to the atmosphere at a temperature of 400 F andatmospheric pressure.

It will be understood that while specific temperatures and pressureswere given to describe a particular embodiment in detail, theseconditions are not restrictive of the invention.

The plant is controlled principally as follows:

A. The turbines run unthrottled, at full capacity, driving thecompressors at constant load to compress air at a constant rate.

B. Excess compressed air is vented to the atmosphere through the vents'79 and 84.

C. The pressure in the chamber ltl is controlled by venting excesscombustion gas to the atmosphere through the vent stack 75.

Further controls include control of the temperature of the gas admittedto the turbines by regulating the amount of auxiliary fuel burned in theboiler and/or by regulating the amount of steam drawn off from the steamdrum, the admission of cooling fluid through the nozzles 71 and 71a intothe gas stream to the turbines to prevent excessive temperatures, e.g.,to hold the gas temperature below 1100 F. to 1250 F., the admission ofquench fluid through the nozzles 95 into the top of the fluidizationchamber to check after-burning; and the cooling of the fluidized bed bythe bed coil 6t Features of the invention, some of which are optional,

are:

The boiler steam drum 17 serves also as a drum for the bed coil 60. Thisreduces the cost involved in the provision of a separate drum for thebed coils.

By locating the boiler on top of the fluidization-combustion chamber theneed for a gas duct between the chamber and boiler is eliminated; alsoeliminated are the need for a boiler stack and the plot area otherwiserequired for the boiler.

By supercharging the boiler the capital cost is reduced in that asmaller and lighter boiler is required and the boiler is more adaptablefor mounting on top of the fluidization-combustion chamber.

Location of the small, last-stage cyclones inside thefluidization-combustion chamber effects a reduction in installationcosts resulting from elimination of piping, valves and separate vesselsto contain the cyclone, in addition to reducing pressure and heatlosses.

It is evident that the use of expansion gas turbinecompressor sets toprovide air for the fluidization-combustion chamber and the boilereifect a reduction in the installed costs resulting from the use ofsimple and inexpensive turbine-compressors and a reduction in operatingcosts resulting from recovery of power formerly vented to theatmosphere.

By locating the turbines and compressors on top of thefluidization-combustion chamber there is a reduction in costs due to theelimination of a turbine-compressor building and the plot area requiredfor such a building.

It will be understood that when the invention is applied to orereduction the compressor 19 is used to compress a fuel-containing gas,such as methane or a mixture thereof with an inert gas, and that thevent 79, if used, would usually be connected to the source reservoir orother suitable receptacle instead of being vented to the atmosphere.

In the modification shown in FIGURE the auxiliary fuel burner is notused. Instead, the clean gas from the fluidization chamber entering thecombustion chamber 47a passes through a series of catalyst grids 98 and99 coated with platinum or other suitable oxidation-promoting catalystfor effecting combustion. The supplemental air from the pipe 50 is mixedwith gas discharged from the chamber by distributor pipes 100 and 101each having a flow-control valve 102 or 103. Although the supplementalair is shown to be added after the discharged gas has passed through thecyclone separators, this is not essential. The further combustioninduced by the catalyst produces hot combustion gas which heats theboiler tubes by radiation and convection as previously described. Weclaim as our invention:

1. In the process of regenerating spent, finely divided metal oxidecracking catalyst bearing carbonaceous deposits, wherein said spentcatalyst is continuously admitted into a closed fluidization-combustionzone, fluidizing-combustion air is continuously flowed upwardly throughsaid catalyst to form a fluidized bed, said carbonaceous deposits areburned to produce an exit gas which is discharged from the top of saidbed and contains entrained catalyst, carbon dioxide and carbon monoxide,said exit gas being incapable of self-sustained combustion at the exittemperature when mixed with supplemental air, and regenerated catalystis continuously discharged from said zone, the improvement of recoveringheat and work energy from said exit gas sufiicient to supply the saidfiuidizing-combustion air by a combination of steps which includes:maintaining said fluidization-combustion zone at'a substantialsuperatmospheric pressure sufiicient to permit expansion of the exit gasin a gas turbine, substantially separating said entrained catalyst fromthe exit gas by inertia without substantially lowering the exit gastemperature, mixing the resulting clean gas with supplemental air,subjecting the resulting mixture to oxidizing conditions within a boilerhaving fluid-confining heat-transfer walls to cause further combustionin the clean gas with oxidation of the carbon monoxide and therebyheating said heat-transfer walls by radiation and convection, expandingthe clean gas in expansion gas turbine means and thereby generatingshaft power, compressing said fluidizing-combustion air to saidsuperatmospheric pressure by using said shaft power, and admitting thecompressed air into said fluidization-combustion zone.

2. Process according to claim 1 wherein said clean exit gas is mixedwith the supplemental air and subjected to said further combustion inthe boiler at substantially the said superatmospheric pressure and priorto expansion in the turbine means.

3. Process according to claim 1 wherein said turbine means is operatedat substantially constant power output by venting a variable amount ofthe exit gas from the fluidized bed after separation of entrained solidstherefrom and prior to expansion in the turbine means.

4. Process according to claim 3 wherein said fluidizingcombustion air iscompressed at a rate in excess of the influx to thefluidization-combustion zone, and the compressed air is admitted intosaid zone at a desired rate by venting a controlled amount thereof.

5. Process according to claim 1 wherein said fluidizingcombustion air iscompressed at a rate in excess of the influx to thefluidization-combustion zone, and the compressed air is admitted to saidzone at the desired rate by venting the excess thereof at a controlledrate.

6. Process according to claim 1 wherein said step of subjecting themixture to oxidizing conditions includes burning auxiliary fuel with aportion of said supplemental air and mixing the resulting hot combustionproducts with the said clean exit gas and supplemental air to bring thesaid mixture to oxidizing temperature.

7. Process according to claim 1 wherein said step of subjecting themixture to oxidizing conditions includes flowing said mixture of cleanexit gas and supplemental air in contact with an oxidation catalyst.

8. In the process of regenerating spent finely divided metal oxidecracking catalyst bearing carbonaceous deposits, wherein said spentcatalyst is continuously admitted into a closed fluidization-combustionzone, fluidizing-combustion air is continuously flowed upwardly throughsaid catalyst to form a fluidized bed, said carbonaceous deposits areburned to produce an exit gas which is discharged from the top of saidbed and contains entrained catalyst, carbon dioxide and carbon monoxide,said exit gas being incapable of self-sustained combustion at the exittemperature when mixed with supplemental air, and regenerated catalystis continuously discharged from said zone, the improvement of recoveringheat and work energy from said exit gas suflicient to supply thecombustion and fluidization air requirements of the process by:maintaining said fluidization-combustion zone at a substantialsuperatmospheric pressure sufiicient to permit expansion of the exit gasin a turbine, substantially separating said entrained catalyst from theexit gas by inertia without substantially lowering the exit gastemperature, mixing V the clean exit gas with supplemental air,subjecting the resulting mixture to oxidizing conditions substantiallyat I said superatrnospheric pressure Within a boiler havingfluid-confining heat-transfer walls to cause further combustion in theclean gas with oxidation of the carbon monoxide and thereby heating saidheat-transfer wall by radiation and convection, discharging theresulting combustion products from the boiler and expanding them inexpansion gasturbine means and thereby generating shaft power,compressing said fluidizing-combustion air and supplemental air to saidsnperatmospheric pressure and supplying them to thefluidization-combustion Zone and the clean exit gas by using said shaftpower.

9. In an integrated plant for the continuous combustion of fuel whichcomprises: a vertically elongated fluidization-combustion chamberincluding a top closure and adapted to confine gas at a substantialsuperatmospheric pressure suflicient to permit expansion of said gas ina turbine; means for admitting finely-divided solids and one combustionreactant to said chamber; gas inlet means for admitting a fluidizing gascontaining the other combustion reactant under said superatmosphericpressure into a lower part of the chamber at a controlled rate forfluidizing id said solids and effecting combustion to produce an exitgas containing entrained solids; a Wall structure defining agas-distributing compartment within the upper part of said chamber;cyclone separator means within said chamber situated beneath said Wallstructure and including an intake communicating with the space withinthe chamber 1 outer tube'being provided with solids-discharge means.

10. In combination with the plant according to claim 9, a collectinghopper Within said chamber for receiving the solids from said smallcentrifugal separators and a solids discharge duct connected to saidhopper and extending out of the fluidization-combustion chamber.

No references cited.

1. IN THE PROCESS OF REGENERATING SPENT, FINELY DIVIDED METAL OXIDECRACKING CATALYST BEARING CARBONACEOUS DEPOSITS WHERIN SAID SPENTCATALYST IS CONTINOUSLY ADMITTED INTO A CLOSED FLUIDIZATION-COMBUSTIONZONE, FLUIDIZING-COMBUSITO AIR IS CONTINUOUSLY FLOWED UPWARDLY THROUGHSAID CATALYST TO FORM A FLUIDIZED BED, SAID CARBONACEOUS DEPOSTIS AREBURNED TO PRODUCE AN EXIT GAS WHICH IS DISCHARGED FROM THE TOP OF SAIDBED AND CONTAINS ENTRAINED CATALYST, CARBON DIOXIDE AND CARBON MONOXIDE,SAID EXIT GAS BEING INCAPABLE OF SELF-SUSTAINED COMBUSTION AT THE EXITTEMPERATURE WHEN MIXED WITH SUPPLEMENTAL AIR, AND REGENERATED CATALYSTIS CONTINUOUSLY DISCHARED FROM SAID ZONE, THE IMPROVEMENT OF RECOVERINGHEAT AND WORK ENERGY FROM SAID EXIT GAS SUFFICIENT TO SUPPLY THE SAIDFLUIDIZING-COMBUSTION AIR BY A COMBINATION OF STEPS WHICH INCLUDES:MAINTAINING SAID DLUIDIZATION-COMBUSTION ZONE AT A SUBSTANTIALSUPERATOMSPHERIC PRESSURE SUFFICIENT TO PERMIT EXPANSION OF THE EXIT GASIN A GAS TURBIN, SUBSTANTIALLY SEPARATING SAID ENTRAINED CATALYST FROMTHE EXIT GAS BY INERTIA WITHOUT SUBSTANTIALLY LOWERING THE EXIT GASTEMPERATURE, MIXING THE RESULTING CLEAN GAS WITH SUPPLE-